This invention relates to a process for the production of particulate sulfur and, more particularly, relates to a method for reducing interruption in the flow of molten sulfur from spray means in the prilling and granulation of sulfur.
Sulfur is recovered in large quantities from sulfur deposits, usually as Frasch sulfur, and from natural gas, usually by the Claus Process. The recovered sulfur is often processed into suitable forms for the market either directly from the recovery process or from impounded areas if the sulfur is stored in solid form in impounded areas at plant sites. Suitable forms of elemental sulfur are slab sulfur or particulate sulfur such as slate, flakes, pellets, granules and prills.
The prior art discloses a number of processes for the production of particulate sulfur, such as by prilling or granulation. A review of these processes, which are used on a commercial scale or are now being developed in the sulfur industry, is published in Sulphur No. 142, May, June, 1979, pages 30-39. More specifically, the prilling of sulfur in a liquid has been disclosed, for example, in U.S. Pat. No. 3,504,061, H. J. Elliott, Mar. 31, 1970. Granulation processes for sulfur have been disclosed in U.S. Pat. No. 3,231,413, Y. F. Berquin, Jan. 25, 1966, according to which sulfur is granulated in a spouted, fluidized bed, and in U.S. Pat. Nos. 3,936,534 A. H. Schallis, Feb. 3, 1976, 4,234,318, J. T. Higgins, et al, Nov. 18, 1980, and 4,272,234, S. Y. H. Tse, June 9, 1981, according to which molten sulfur is sprayed from one or more nozzles onto solid particles of sulfur in a rotating drum. In all these processes, molten sulfur is directed through means having one or more orifices from which the molten sulfur emanates in a flow of droplets or as a spray.
I have observed that the processes for production of particulate sulfur, particularly from Claus Process sulfur, suffer from interruptions in the flow of molten sulfur emanating from spray means such as spray nozzles and prilling devices, and produce a relatively large amount of undesirable fines. The flow interruptions interfere with the continuity of the process, while fine sulfur particles formed during the process are difficult to handle and control, and are often discharged from the process as an undesirable emission. In addition, in the prilling of sulfur in a countercurrent flow of air, undesirable fines discharge partly with the prills and partly with discharged cooling air, to make the prilled product less uniform in size necessitating screening and remelting of the fines for recycling, and to cause undesirable and visible sulfur emission.